Olympic champion Andy Murray advanced to the last eight at the US Open while World No. 1 Roger Federer reached his 34th consecutive Grand Slam quarter-final on Monday without touching a racquet.

British third seed Murray, seeking his first Grand Slam title after four runner-up finishes, defeated Canadian 15th seed Milos Raonic 6-4, 6-4, 6-2 in a night match at Arthur Ashe Stadium.

The 25-year-old Scotsman, who reached his eighth Grand Slam quarter-final in a row, will play for a semi-final berth against Croatian 12th seed Marin Cilic, who beat Slovakian Martin Klizan 7-5, 6-4, 6-0.

Murray is 6-1 lifetime against Cilic but the only loss came in the fourth round of the 2009 US Open.

"Tough match. He's a tough player," Murray said. "He works extremely hard. He has a solid game. I will have to work extremely hard to beat him."

Top seed Federer, seeking an unprecedented 18th Grand Slam title and record sixth US Open crown, advanced by walkover when American Mardy Fish withdrew from their match over health concerns.

"I am really sorry for Mardy," Federer said. "I just want to wish him a speedy recovery. We all want to see him back on tour soon."

Federer has earned 38 career quarter-final Grand Slam appearances, three shy of the Open-era record 41 achieved by American Jimmy Connors.

"It will be a tough match against Tomas," Federer said. "We have played many times in the past and he has always been a tough opponent. I will have to continue to serve well and dictate the points."

Murray broke Raonic with a drop volley winner for a 5-4 lead and held to take the first set after 36 minutes. In the second set, Murray broke for a 3-2 edge when Raonic netted a forehand and held serve from there to seize command.

Raonic, trying to become the first Canadian man in a Grand Slam last eight in the Open era, surrendered breaks in the third and fifth games of the final set.

Murray, who never faced a break point, held serve to end matters after two hours with a service winner.

"I used a lot of variation," Murray said. "Milos has a huge game, massive serves. I guessed right a couple times, got lucky and was able to hit a few passing shots on him.

"I was just trying to react as fast as I could. Sometimes they fly past you and sometimes you get a racquet on it. Tonight I got a racquet on it."

Fish, 30, missed two months earlier this year with a heart problem after his heart rate increased to three times its normal resting pace. He underwent a cardiac catheter ablation in Los Angeles on May 23 to treat his condition.

But his statement about the withdrawal did not specify a reason.

"I regret that I have to withdraw from the US Open for precautionary measures. I was reluctant to do so, but am following medical advisement," Fish said. "I had a good summer and look forward to resuming my tournament schedule in the fall."

Federer, who won his 17th Grand Slam title in July at Wimbledon, has not dropped a set in the Flushing Meadows fortnight.

"I probably need to have something more than 100 percent," Berdych said.

Berdych, who took only two hours to reach his first US Open quarter-final, has won three of his past six meetings with Federer, including a US Open tuneup last year at Cincinnati and a 2010 Wimbledon quarter-final.

Berdych finally reached the US Open last eight after 10 tries with his 200th career hardcourt triumph. He joined Petr Korda and Ivan Lendl as the only Czech men in the Open era to have reached the quarter-finals at all four Grand Slams.

"It helps my confidence," Berdych said.

Almagro, 27, hopes to replace injured Rafael Nadal on the Spanish Davis Cup team that will host the United States next week in a semi-final tie.

"Knowing Rafa like I know him, he will be climbing the walls," Almagro said. "The most important thing is that he will have time to recuperate so he will come back the same player that he was."

Berdych, whose best Grand Slam result was a 2010 Wimbledon final loss to Nadal, improved to 7-3 lifetime against Almagro and snapped a five-game losing streak to top-20 rivals dating to a Rome victory over Almagro last May.

Cilic took his eighth victory in a row over a left-handed foe.

"I like to play them," he said. "That game suits me. I play well from both sides so it's hard for them to find an opening."